This invention relates to the floatation of matter at the surface of a liquid medium to assist its separation and is particularly, but not necessarily exclusively, concerned with the floatation of actinides in magnesium hydroxide based media.
In the reprocessing of nuclear fuel elements it is necessary to first separate the spent fuel from its cladding. For fuel which has been irradiated in the so-called Magnox reactors, the cladding is made from Magnox, a magnesium alloy containing small quantities of aluminium, manganese and zirconium. Once the cladding has been removed it is transferred to concrete silos where it is stored under water. Small quantities of spent fuel matter, that is uranium dioxide and traces of other actinide oxides become associated with the cladding and are therefore transferred to the storage silos.
During prolonged storage under water the cladding reacts with the water to give a magnesium hydroxide based sludge. The sludge also contains the particles of spent fuel that were associated with the cladding. Sludges containing actinides are also encountered in other industries, such as the uranium mining industry. It is desirable to remove the particles of spent fuel and/or actinides from such sludges.
The aim of the present invention is to provide a method of separating matter by floatation.